President Barack Obama is prepared to act without Britain, officials said, noting that unlike U.S. involvement in the 2011 military operation in Libya, the options under consideration in Syria are smaller-scale and wouldn’t require a coalition to be effective.

“Here, what’s being contemplated is of such a limited and narrow nature that it’s not as if there’s a similar imperative for bringing in different capabilities from different countries,” a senior administration official said. “We believe it’s important that there be diplomatic support from key allies, and we think we’re getting that.”

If the operation is “limited and narrow” enough, it could obviate not only the need for British support, but also the constitutional requirement of congressional authorization, which only applies to offensive action large-scale enough to qualify as a “war” (setting aside the difficult question of the exact point at which a military engagement becomes big enough to be a “war.”) The problem is that a very small-scale action might not actually be enough to accomplish anything – especially if Assad and his government know in advance that a small-scale attack is all they have to worry about. If Assad believes that using chemical weapons and killing large numbers of civilians are necessary for him to stay in power, he’s unlikely to stop just because we hit him with a minor attack that he knows will soon end. If, on the other hand, Obama intends to launch a larger offensive should the small one fail, then both proper constitutional authorization and allied support would be desirable.

It’s hard for me to say whether the only available options are either a constitutionally permissible attack too small to do any good, or a bigger operation that doesn’t have enough political support to get the congressional authorization needed to make it legal. Perhaps there is some brilliant middle option that doesn’t occur to me. On the other hand, it’s also possible that even a larger operation will cause more harm than good, if by weakening Assad it strengthens a rebellion that is increasingly led by radical Islamist jihadists.